1. Field of the Invention
The present invention relates to an expansion valve and, more particularly to a vibration-proof spring suitable in preventing the vibration of an actuating member of the expansion valve.
2. Description of the Related Art
A refrigeration cycle in an automotive air conditioner is generally configured such that it includes a compressor, a condenser, a receiver, an expansion valve, and an evaporator. The compressor compresses a circulating refrigerant. The condenser condenses the compressed refrigerant. The receiver separates the condensed refrigerant into a gas and a liquid. The expansion valve throttles and expands the separated liquid refrigerant and delivers it by turning it into a spray. Then the evaporator evaporates the misty refrigerant and thereby cools the air inside a vehicle by the evaporative latent heat.
Used as the expansion valve is a thermostatic expansion valve which senses the temperature and pressure of refrigerant in an outlet side of the evaporator such that the refrigerant delivered from the evaporator has a predetermined degree of superheat and which controls the flow rate of refrigerant delivered to the evaporator by opening and closing a valve section. This thermostatic expansion valve includes a body formed with a first passage for passing the refrigerant flowing from the receiver to the evaporator and a second passage for passing the refrigerant returning from the evaporator and supplying the refrigerant to the compressor. A valve hole is formed midway in the first passage. And a valve element is provided in a predetermined manner such that the flow rate of refrigerant flowing to the evaporator is regulated by touching and leaving the valve hole. Provided at an end of the body is a power element that senses the temperature and pressure of refrigerant flowing through the second passage and controls the valve opening degree of the valve section. The drive force of the power element is transmitted to the valve section by way of an elongated shaft. The shaft extends in such a manner as to move across the second passage and reaches the first passage and is slidably supported by an insertion hole formed in a partition that separates the first passage from the second passage.
In such an expansion valve as describe above, the pressure may fluctuate in an upstream side where a high-temperature refrigerant is introduced. If this problem of fluctuation is left unattended, the valve element may vibrate and generate noise. In the light of such problems, the following method is often employed. That is, the biasing force of a spring is applied to a shaft from its lateral side so that the valve element does not respond sensitively to the fluctuation in pressure, thereby possibly stabilizing the operation of the valve element. For example, a plurality of plate-like bodies are cut out inwardly from an annular section of a support ring, thereby producing a vibration-proof spring (see Reference (1) in the following Related Art List, for instance). Also, as in an example of Reference (2) in the Related Art List, a vibration-proof spring is formed by bending a wire for use with spring.